High speed means and method for coating
and drying thin paper webs



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HIGH SPEED MEANS AND METHOD FOR COATING AND DRYING THIN PAPER WEBS Filed Oct. 11, 1965 5 Sheets-Sheet 5 IHUfdill!!!- FIG. 3

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5y M/wca w; z WE/1/S7E/MADM/N/STRATOR ATTORNEYS United States Patent C) 3,311,499 HIGH SPEED MEANS AND METHOD FOR COATEJG AND DRYING THIN PAPER WEBS Thomas W. Busch, Appleton, Wis., and Abraham Lewenstein, deceased, late of Appleton, Wis, by Marceline Lewenstein, administrator. Appleton, Wis, assignors to Appleton Coated Paper Co., Appleton, Wis, a corporation of Wisconsin Filed Oct. 11, 1965, Ser. No. 495,378 12 Claims. (Cl. 117119.8)

This application is a continuation-in-part of our copending application Ser. No. 187,439, filed Apr. 13, 1962, and entitled, High Speed Means and Method for Coating and Drying Thin Paper Webs, now abandoned.

This invention is addressed to the coating of one side of a continuous web of thin paper with a composition in the form of a polyphase system in which the continuous phase contains a binder and a dispersed phase which is adapted to be secured by the binder to the surface of the paper web to form the applied coating in which the dispersed phase remains uniformly distributed in the bonded coating when dried. The invention has application primarily to the high speed drying of aqueous coatings on thin paper wherein the coating is formed of encapsulated color-containing liquids dispersed with cellulosic particles in the aqueous medium to form coatings of the type in which it is dificult to form a smooth uniform coating free of wrinkles, crimp and curl upon drying. Coatings of the type described have various uses and applications, such as in the manufacture of protective papers, decorative paper, adhesive coated papers, printing papers, reproduction papers, artists mats and the like papers which are emulsion or dispersion coated to produce a polyphase system as a coating on the paper surface.

it is desirable, in a system of the type described, to strive for maximum output with minimum cost from the standpoint of expenditure of time, materials, equipment and labor, thereby to increase the capacity of the manufacturing facility while making coated papers of the type described available at lower cost. While these objectives represent the intent of all normal research and development, their attainment presents a number of unique problems when confined to the fabrication of coated papers with a composition of the type described. For example, it has been found that the drying of the coating is closely related to the distribution of the materials embodied within the coating composition whereby non-uniformities can develop as between materials forming the dispersed phase and a continuous phase or the binder with which the dispersed phase is anchored to the paper surfaces. Such non-uniformities in distribution oftentimes result in segregation of the materials making up the various phases whereby the binder, when concentrated at the surface, can bar ready access to the dispersed phase, or when concentrated at the base, will insufliciently bond the dispersed phase in the coating. Conversely, concentration of the dispersed phase at the base may lead to insufficient bond between the coating and the paper, while concentration of the materials making up the dispersed phase at the surface can institute other difliculties in use. It has also been found that the coating and drying of webs of thin paper coated with a composition of the types described often leads to problems of excessive curling or wrinkling of the finished coating web by reason of the stretch that is permitted when the paper fibers are wet with the coating and/ or the high shrinkage that takes place during drying of the applied emulsified coating composition.

It is desirable to provide for a coating of uniform ice thickness having a desirable uniform distribution of materials therein. It is also desirable to achieve the application of a thin and uniform coating onto the continuous web of thin paper without introducing curling, rippling or wrinkling in the coated paper during the drying operation and wherein the diluent is eliminated at a controlled rate for the deposit of the solids in uniform dispersion in the bonded coating that is formed on the one side of the paper web.

It is towards an increase in the rate of production of the coated paper without handicapping the qualities or the characteristics of the coating that considerable research and development has been expended, and it is an object of this invention to provide a new and improved paper coating means and drying method which achieves the objectives heretofore described.

More specifically, it is an object of this invention to provide a method and means for treatment of continuous webs of thin paper with a polyphase system embodying a dispersed or emulsified phase in an aqueous medium, as the continuous phase, and wherein the aqueous medium preferably though not necessarily contains a binder component to produce a bonded coating upon drying, and wherein the materials forming the dispersed phase are uniformly distributed throughout the bonded coating; in which the coating and drying is carried out at a high rate of speed; in which the coating is dried on the surface of the paper without causing curling of the paper, or ripples or wrinkles or other imperfections; which can be economically carried out with minimum cost from the standpoint of labor, materials and equipment; and which produces a coated product of good quality.

These and other objects and advantages of this invention will hereinafter appear and, for purposes of illustration, but not of limitation, an embodiment of the invention is shown in the accompanying drawings, in which- FIGS. 1, 2 and 3 constitute a complete flow sheet of the machine illustrating the means and method for the application and drying of the coating from the time that the web is paid out from the feed rolls to the time that the coated web is dried and rewound on the wind-up rolls.

Before entering into a description of the invention, it will serve briefly to describe the type of composition which presents coating and drying problems sought to be overcome by the practice of this invention. Briefly described, such composition comprises an aqueous emulsion or dispersion wherein the materials forming the dispersion phase constitutes the major component of the dried coating, and wherein the aqueous medium forming the continuous phase embodies a binder which, when the coating is dried, serves to bind the coating to the surface of the paper web. As previously pointed out, some of the problems result from the stretchability of the paper web when the fibers are wet with water, and the shrinkage of the web when the water is removed whereby when the web is dried under tension the final product is characterized by excessive wrinkling and curling. Another of the problems is the shrinkage that tends to be introduced into an emulsion coating of the type described upon heating to remove diluent and set the materials in the coating. Unless the web is in a relaxed state during drying, such shrinkage characteristics have been found to introduce the tendency to wrinkle and curl the coated web. Such difficulties have been encountered most often in an emulsion and dispersion system wherein the materials forming the dispersed phase represents 15 to 25 parts by weight per 85 to parts by weight of the aqueous or other volatilizable diluent comprised mostly, if not entirely, of water.

An important concept of this invention resides in the balancing of the formulation of the coating composition, the application of the coating composition onto the web of thin paper with the rate of removal of the volatiles to deposit a dried coating in which the materials forming the dispersed phase are maintained in the desirable distribution throughout the coating that is formed on the paper upon drying. It has been found that removal of the volatiles at too high a rate, in the attempt to achieve high coating speeds, often results in such redistribution of ingredients as enables the binder, such as starch, casein or the like, to concentrate in the surface portions of the coating to overlie the materials making up the dispersed phase whereby such materials are no longer readily accessible. There is also reason to believe that the increase in the rate of evaporation to increase coating speed results in the unequaled removal of aqueous medium through the cross section of the coating whereby the surface portions, containing less moisture than the remainder, rise in temperature before the remainder, with the result that the materials in the surface portion are subjected to excessive heat thereby to cause hardening of the binder or other possible undesirable reactions.

Through extensive experimentation, it has been found that the evaporation rate of a coating composition of the type described and provided in accordance with the practice of this invention should not exceed 5.5 pounds of water per square foot per hour. For a coating composition containing 18 percent solids and applied coating weights of 4 /2 pounds per 3300 square feet of surface area onto paper traveling 'at a rate of 2000 feet per minute, a drying section of 144 feet in length is desired.

Having described the coating composition and its characteristics, reference will now be made to the method and means for application of the coating composition onto a thin web of paper and the removal of volatiles to produce a dried coating of good quality. As the substrate, use can be made of paper, such as a base paper having a basis weight of 33 pounds for five hundred 25" x 38" sheets, which may or may not be back coated with a clay enamel or the like.

The combination of elements hereinafter described with reference to the drawing has been arranged to achieve the objective of maximum rate of coating and drying with optimum conditions from the standpoint of the characteristics and properties of the coated paper, including the desired thickness and uniformity of coating, the desired distribution of solids within the dried coating, the freedom of curl, blisters, crags and the like imperfections in the coated paper coupled with high pick resistance and ink absorption in the coated surface.

Referring now to the drawing, the numeral represents the stand which rotatably mounts the unwind bracket 12. on which feed rolls 14 are mounted for the supply of paper to be coated. From the feed roll 14, the web 16 of paper is threaded about a plurality of staggered tensioning rolls 18 which are mounted for free rotational movement on shiftable supports 20 spring tensioned to equalize the rate of advancement of the web from the feed rolls to the coating drying end section.

From the equalizing rolls 18, the web 16 passes about a lead-in roll 22 to the coating roller 24 the bottom portion of which projects downwardly into a pan 26 containing coating composition at a level to wet the periphery of the coating roll in advance of contact with the underside of the web of paper for transfer of coating composition from theperiphery of the coating roller to the contacted surface of the paper web.

To maintain uniformity in the amount of coating composition transferred from the coating roller 24 to the underside of the paper web, it is desirable to provide for uniform contact between the periphery of the roller and the paper across the entire width thereof as well as lengthwise with the different portions of the web of paper. For this purpose, there is provided an air nozzle 28 vertically aligned with the coating roller with the outlet of the nozzle directed downwardly onto the top surface of the paper whereby the air jet issuing from the nozzle across the entire width of the web of paper operates effectively to hold down the web of paper onto the periphery of the coating roller. Thus a uniform layer of coating composition is insured notwithstanding the linear travel of the web at high speed over the coating roller. Between the coating roller 24 and an air knife 35 the wet coating previously applied to the surface of the web of paper is engaged by a roller 32 which is rotated in a direction whereby the peripheral portion in engagement with the applied coating travels in an opposite direction. The reversing roll 32 operates to iron out disagreeable patterns acquired by the coating before the coating is engaged by the air blade of the air knife 3% to remove excess coating and to smooth the coating composition applied to the surface of the web of aper.

The air knife 30 is of conventional construction and it is mounted to direct 'an air blade angularly downwardly onto the a plied coating to remove excesses of coating composition and to smooth the coating on the web as it travels about the roller 34.

For high speed production, it is desirable further to work the applied coating after cutoff by the air knife and before drying sets in. This is achieved by an additional set of rolls between which the coated web is adapted to pass. The Working rolls comprise at least two longitudinally spaced apart rolls 36 and 38 facing the coated side of the -web of paper and an intermediate roller 40 facing the back side of the web of paper whereby in response to tangential adjustment of the rollers in the direction towards and away from the web, the area of contact between the periphery of the rollers and the coated side of the paper can be varied.

The smoothing rolls 36 and 38 are operated for rotation of the surface in a reverse direction with respect to the direction of travel of the web. It has been found that a close relationship exists between the peripheral speed of the smoothing rolls and the linear rate of travel of the web with the peripheral speed in the reverse direction being somewhat proportional to the linear speed of the web. Thus, it is desirable to increase theperipheral speed of the smoothing rolls in response to increase in the linear speed of the web of paper and vice versa. Instead of increasing peripheral speed, the desired effect can also be achieved by the increase in the area of contact between the rolls and the web of paper or by a combination of speed adjustment and area of contact.

From the smoothing section, the coated web passes over the idler roller 42 into the high speed drying section which will hereinafter be described wherein the volatiles are removed from the applied coating at a rate which is calculated not to exceed 5.5 pounds of water per square foot per hour but at a rate which continues to insure the desired uniform distribution of solids in the applied coating. From the drying section, the finished web passes over the guide rolls 46 into a bank of tensioning rolls 48 to the wind-up roll 50 rotatably mounted on the swivel bracket 52 supported on the standard 56.

An important concept of this invention resides in the construction and operation of the drier section wherein water removal is effected from the dispersion coating at a desired rate for good coating quality and without curl or ripple in the coated sheet or without blisters or crags in the dried coating. The desired results are achieved by a combination of conditions including travel of the coated web in an arcuate path which is convex, when viewed from the coated side, through the drier whereby curl is minimized in the sheet during drying. The desired results are also achieved by the combination which includes continuous support and conveyance of the coated web of thin paper throughout substantially its entire length and width during travel through the drying section whereby the coated web is able to remain in a relaxed state during the drying of the coating and wherein the support and conveyance is achieved by the use of a porous belt which is capable of maintaining its strength and flexibility in the temperature conditions existing and is also able to breathe to avoid the entrapment of moisture or other volatiles released from the coating. The desired results are further achieved by the combination which includes the subdivision of the drier section into longitudinally separated compartments with individual means in each compartment for the direction of hot drying air onto the coated surface for the purpose of controlling the character and the rate of water removal whereby the drying rate and the desired drying conditions can be maintained.

Travel of webs of coated paper in an arcuate path through a drier to minimize curl has previously been employed except that use has been made of an arc of only 100 feet radius for drying gummed paper or an arc of about 200 feet in radius for the application of a decalcomania coating. It has been found that drying at the desired high rate of linear speed can be achieved without curl and without other difficulties when the web is advanced through the drying oven through an arcuate path having a radius greater than 250 feet and preferably through an arc having a radius of from 300 to 350 feet. Under such conditions a high speed production can be achieved without curl and without ripple in the final product.

With reference to the continuous support of the web during its travel through the arcuate path in the drying section, carriers of the type heretofore employed have been found to be inadequate for proper support and conveyance of the coated web through the drying section. For example, spaced rollers are incapable of sufficient support to minimize the introduction of wrinkles into the web by reason of the tensions existing when the web of thin paper is pulled through the drying section. Further, spaced rollers permit portions of the web located between the rollers to sag by reason of its own weight and by reason of the blasts of hot air directed downwardly onto the top coated side of the web of paper for drying. Such variations in the distances between the drying air nozzles and the coated surfaces of the web introduce many variables whereby an inferior product would be secured in a high speed operation.

In the attempt to overcome the deficiencies of spaced rollers for support, attempts have also been made to employ a continuous support in the form of a stationary metal arch employing an air blanket between the paper and the support to minimize drag. Such fixed metal arch introduced difficulties occasioned by the drag and the friction between the two surfaces which were subject to relative movement and it was incapable of eliminating the problems resulting from tension or wrinkling although it did function to improve the stabilization of the web with reference to the air nozzles.

he deficiencies heretofore pointed out have been overcome, in accordance with the practice of this invention, by the use of a continuous support and conveyor in the form of an endless belt 68' on which the coated web 16 rests and by which it is carried through the drying section so that the coated web is caused to travel at the same linear speed with the belt through the drying section. It has been found that best use can be made of an endless belt which is capable of high strength and high tension under the operating conditions existing within the drying oven; which is flexible and resilient for equalization of tension and turning about relatively small radii; which is capable of breathing thereby to enable the passage of moisture, vapor or air therethrough, and which is capable of support to carry the thin coated paper web while permitting sufiicient relative movement as will enable the coated web to expand when wet and contract upon drying without causing the introduction of wrinkles or curls in the web. The characteristics described have been 6 achieved in a continuous belt woven of a mixture of asbestos, synthetic polyester resin (Dacron) and cotton. In use, the fibers are woven into plies having a total thickness of about 0.15 inch which consists of three plies combined to form a belt capable of excellent use in the practice of this invention.

Referring now to the drawings, it will be seen that the dryin section is provided with an upper set of longitudinally spaced apart rollers 62 arranged to define an arcuate path through the drier for a radius of about 340 feet. Spaced a short distance between the upper set of rollers 62 is another set of rollers 64 arranged in substantially parallel relation therewith, although parallelism is not essential. The endless belt 60 travels through the drying section over the upper rolls 62 until it passes over the end roll 46 located beyond the drier housing after which it leaves the path of the web and runs downwardly about the idler roller 66 and then up and down about the stern of take-up rollers 63 to the set of rollers 64 over which the belt travels for return to the inlet end of the drier housing. The take-up rolls are operated by an air cylinder for vertical adjustment to maintain a predetermined tension in the belt.

At the inlet end, the belt travels downwardly from the face of the lower set of rolls 6d and passes about the idler roller 42 at which point it meets the coated web for support of the coated web on the top side thereof during travel through the drier housing 70.

The longitudinally separated compartments of the drier are provided with separate blowers 72, 74, 76, 78, 8t) and 82, respectively, which are adapted to introduce the hot drying air at selected temperatures for balanced moisture removal at the optimum rate for high speed production. The hot air and vapor removed from the coating is exhausted from the housing 70 through outlets 8:} and 823 fitted with exhaust fans so that the hot air and vapor is drawn from the extremities towards the central portion of the dried thereby to minimize exhaust into the coating or drying room.

it will be apparent that the temperature conditions to which the coated paper is exposed will result in simultaneous release of vapors from the bottom side of the paper during travel through the drier section. Because of the porous nature of the endless belt on which the web is continuously supported, such vapors are capable of full dissipation without interference with the drying operation and without causing defects to be formed in the coated web. The use of the continuous belt traveling with the paper for support has also been found to be instrumental in eliminating a number of problems that would otherwise exist in the handling of light weight paper in such high speed operation.

One of the important concepts of this invention resides in the combination of the coated paper web and the endless porous belt on which it is carried. Because of the weight of the coated paper and the reaction to the drying air stream directed downwardly onto the coated surface of the web, the coated web is placed in intimate contact with the surface of the belt whereby the belt serves not only continuously to support the coated web but aslo to carry the coated web as the principal driving means through the drying section. Thus the coated paper is able to rest in a relaxed state on the surface of the belt during its travel through the drying oven so that expansion and contraction can take place without the wrinkling normally encountered and so that pulling tension often employed for effecting continuous travel of the web through the drying section can be avoided with corresponding elimination of tension problems such as wrinkling.

It was found that without the continuous belt support, conveyance of the coated thin paper web through the long drying oven could not be obtained to prevent a catenary formation of the type usually experienced when the web is carried between spaced supports and when 7 the web is exposed to the forces of the high velocity drying air impinging upon its top surface.

The combination of coating application, drying and Web conveyance techniques employed in accordance with the practice of this invention has been found to be instrumental in enabling marked increase in the speed of application and drying of an emulsion or dispersion coating of the type described thereby materially to increase the rate of output of a commercially desirable, coated, thin paper product with corresponding decrease in cost.

While not illustrated in the drawing, it will be understood that the coating device described will employ separate drive means for the unwinding and Winding rolls 14 and 52, for the reversing roll 32, the smoothing rolls 36 and 3%, as well as for the belt operation. As illustrated in the drawings, the endless belt which supports the coated web during its travel in the arcuate path through the drier housing extends beyond the inlet and the outlet to the housing to support the coated web thereon more properly to locate the coated web thereon before entrance into the housing and after exit from the housing.

It will be understood that numerous changes may be made in the details of construction, arrangement and operation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. A high speed drier for drying thin webs of paper Wet on one surface with a coating composition in the form of an aqueous emulsion of microscopic capsules containing a marking fluid and interspersed with smudge reducing cellulosic fibers to produce a smooth uniform dry coated web which remain substantially flat, comprising an elongate horizontally disposed housing having an inlet at one end and an outlet at the other, an endless supporting belt of porous material providing a continuous supporting surface extending horizontally through the housing with the upper run of the belt supported to travel through a convex path having a radius of at lea-st 259 feet, driving means operatively connected to the continuous belt for linear displacement thereof through the hous- 1 ing at a uniform rate, means for positioning the coated web with the coated side uppermost on the top side of the upper run of the belt whereby the coated Web is continuously supported and carried by said belt for travel through the housing in a relaxed state on the surface of the belt and means for advancing the coated web onto the belt at the same linear speed as the belt for travel therewith through the housing, and means for projecting hot drying gases onto the top side of the coated paper web during passage through the housing to volatilize off the diluent from the applied coating composition during passage through the housing.

2. A drier as claimed in claim 1 which includes spaced rollers subdivided into an upper and lower run with the rollers in the upper run spaced longitudinally one from the other and arranged in an arcuate path through the housing over which the endless belt is threaded for support.

3. A drier as claimed in claim 1 in which the upper run of the endless belt travels through an arc having a radius within the range of 300450 feet.

4. A drier as claimed in claim 1 in which the drier is subdivided longitudinally into sections and which includes air nozzles for each of said sections extending crosswise of the paper web and arranged in longitudinally spaced apart relation above the web and separate hot air feeding means for each nozzle section to control the temperature of the air directed downwardly from the nozzles onto the coated surface of the paper web for elimination of moisture at a rate less than 5.5 pounds per square foot per hour.

5. A drier as claimed in claim 1 in which the supporting belt consists of woven plies formed of a mixture of fibers including asbestos, polyester fibers and cotton.

6. A high speed drier for drying thin webs of paper wet on one surface with a coating composition in the form of an aqueous emulsion comprising an elongate horizontally disposed housing having an inlet at one end and an outlet at the other, an endless supporting belt of porous material providing a continuous supporting surface extending horizontally through the housing with the upper run of the belt supported to travel through a convex path having a radius of at least 250 feet, driving means operatively connected to the continuous belt for linear displacement thereof through the housing at a uniform rate, means for positioning the coated web with the coated side uppermost on the top side of the upper run of the belt whereby the coated web is continuously supported and carried by said belt for travel through the housing in a relaxed state on the surface of the belt and means for advancing the coated web onto the belt at the same linear speed as the belt for travel therewith through the housing, and means for projecting hot drying gases onto the top side of the coated paper web during passage through the hous ing to volatilize off the diluent from the applied coating composition during passage through the housing.

7. The method of high speed drying of thin webs of paper wet on one surface with a coating composition in the form of an aqueous emulsion of microscopic capsules and cellulosic fibers to produce a smooth dry coating on the web which remains substantially free of curl, wrinkles and crimping, comprising the steps of applying the coating composition and forming a layer of uniform thickness on the paper web horizontally, advancing the paper web through a drying zone, supporting the web in a relaxed state during passage through the drying zone on a horizontally disposed surface in the form of an endless belt of porous material which provides a continuous supporting surface of a vapor impervious material advanced at a linear speed corresponding to the linear speed of the coated paper web, arching the top run of the supporting surf-ace for travel through an arcuate path having a radius greater than 250 feet, advancing the surface aud the coated paper Web at substantially the same linear speed through the drying zone whereby the web rests on the top of the supporting surface in a relaxed state during travel through the drying zone to enable the coated web to expand and contract without wrinkling and crimping responsive to the release of moisture during drying, blowing hot air onto the top coated side of the web while at rest on the supporting surface during passage through the drying zone, and maintaining the velocity of the air and temperature to effect removal of moisture from the coating at a rate less than 5.5 pounds per square foot per hour.

The method as claimed in claim 7 in which the supporting surface on which the coated paper web rests during travel through the drying zone is formed with an are having a radius within the range of 300350 feet.

9. The method as claimed in claim 7 in which the supporting surface is in the form of an endless belt formed of fibrous materials which are insensitive to the heat of drying.

19. The method as claimed in claim 7 in which the drying zone is subdivided longitudinally into separate sections and in which the drying air is projected onto the top surface of the belt from separate outlets in each section controlled as to temperature and velocity to effect removal of moisture from the coating at a rate corresponding to less than 5.5 pounds per square foot per hour.

1.1. The method of high speed drying of thin webs of paper wet on one surface with a coating composition in the form of an aqueous emulsion to produce a smooth dry coating on the web which remains free of wrinkles and curl, comprising the steps of applying the coating composition and forming a layer of uniform thickness on the paper web horizontally, advancing the paper web through a drying zone, supporting the Web in a relaxed state during passage through the drying zone on a hori- Zontally disposed surface in the form of an endless belt of porous material which provides a continuous supporting surface of a vapor impervious material advanced at a linear speed corresponding to the linear speed of the coated paper web, arching the top run of the supporting surface for travel through an arcuate path having a radius greater than 250 feet, advancing the surface and the coated paper web at substantially the same linear speed through the drying zone whereby the Web rests on the top of the supporting surface in a relaxed state during travel through the drying zone to enable the coated Web to expand and contract Without wrinkling and crimp ing responsive to the release of moisture during drying, blowing hot air onto the top coated side of the Web while at rest on the supporting surface during passage through the drying zone, and maintaining the velocity of the air and temperature to effect removal of moisture from the References Cited by the Examiner UNITED STATES PATENTS 1,929,877 10/1933 Bonamico 11720 1,956,062 4/ 1934 Duvall 34-155 1,979,346 11/1934 Rappolt et al. 3423 2,130,665 11/1938 Bradner 34162 X FREDERICK L. MATTESON, JR., Primary Examiner.

JOHN J. CAMBY, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,311,499 March 28, 1967 Thomas W. Busch et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 8, lines 29 and 73, strike out "horizontally",

each occurrence; line 30, after "web" insert horizontally same column 8, line 73, after "web", second occurrence, insert horizontally Signed and sealed this 14th day of November 1967.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

6. A HIGH SPEED DRIER FOR DRYING THIN WEBS OF PAPER WET ON ONE SURFACE WITH A COATING COMPOSITION IN THE FORM OF AN AQUEOUS EMULSION COMPRISING AN ELONGATE HORIZONTALLY DISPOSED HOUSING HAVING AN INLET AT ONE END AND AN OUTLET AT THE OTHER, AN ENDLESS SUPPORTING BELT OF POROUS MATERIAL PROVIDING A CONTINUOUS SUPPORTING SURFACE EXTENDING HORIZONTALLY THROUGH THE HOUSING WITH THE UPPER RUN OF THE BELT SUPPORTED TO TRAVEL THROUGH A CONVEX PATH HAVING A RADIUS OF AT LEAST 250 FEET, DRIVING MEANS OPERATIVELY CONNECTED TO THE CONTINUOUS BELT FOR LINEAR DISPLACEMENT THEREOF THROUGH THE HOUSING AT A UNIFORM RATE, MEANS FOR POSITIONING THE COATED WEB WITH THE COATED SIDE UPPERMOST ON THE TOP SIDE OF THE UPPER RUN OF THE BELT WHEREBY THE COATED WEB IS CONTINUOUSLY SUPPORTED AND CARRIED BY SAID BELT FOR TRAVEL THROUGH THE HOUSING IN A RELAXED STATE ON THE SURFACE OF THE BELT AND MEANS FOR ADVANCING THE COATED WEB ONTO THE BELT AT THE SAME LINEAR SPEED AS THE BELT FOR TRAVEL THEREWITH THROUGH THE HOUSING, AND MEANS FOR PROJECTING HOT DRYING GASES ONTO THE TOP SIDE OF THE COATED PAPER WEB DURING PASSAGE THROUGH THE HOUSING TO VOLATILIZE OFF THE DILUENT FROM THE APPLIED COATING COMPOSITION DURING PASSAGE THROUGH THE HOUSING. 